Kers on a MB?

[effoner]

Friend and I been thinkin bout merging gas and electric similar to KERS on an F1 car. KERS, Kenetic Energy Recovery System. I know the electric motors can recharge the battery when braking so using it along with an engine would provide alot of banked power. Using that power as a "power to pass" or boost at will would be far out. Maybe having it geared for top end would be best.
Has anyone done anything like this or am i just thinkin to much. It would get pretty busy with the controls and hardware. Just a thought. Aloha!!

 

[RedBaronX]

if you can harness the braking power and use it to recharge a battery, you would probably come up with enough to power a full lights system. As for running an electric engine, I think the hard part would be getting the two engines to talk to each other-- the electric telling the gas that it's going to take over on the high end...

Possible? It has to be. But I think you would have to count on a lot of manual, user-actuated switching as well. The engine is shut off with an electrical kill switch, but it's started by physically turning it over. You might get the electrical engine to "tell" the gas motor to shut off, but you might have to count on having the rider re-engage the gas engine when it needs to take over...

 

[wheelbender6]

If you ran the electric with the pedal assist sensor rather than a throttle, you could use the electric motor for starting off and save clutch wear.

 

[ibdennyak]

Maybe a master-slave situation. The electric is the prime mover, and the gas is controlled by the state of battery charge. IE, the electric would charge and discharge the battery, which would independently control the charging of the gas engine. I have a couple boards that were suppoeed to do just that somewhere. Problem I had was that the boards were calibrated for 12 volts, and my system was 48 volts. Originally I had planned on sensing off 1 12 volt battery, but I was also drawing off another battery for lights etc, and everything got confusing.....so I took two tylenol and forgot the whole thing.

 

[loquin]

These systems are a form of hybrid gas/electric, and is similar to regenerative braking on EVs.

Modern hybrids/EVs use a planetary gearing scheme, where the gas motor is attached to one of the three transmission 'inputs,' the electric motor/generator to a second 'input' and the wheels to the third 'input.'

With planetary gears, you can stop any one of the three 'inputs' and the other two shafts are 'connected' to each other. Or, you can apply power to two of the three shafts, and route the sum of the two shafts to the third. Or the reverse.

So, for a KERS system, do the same thing. MG to one input of a planetary gear, gas motor to a second input, and sprocket on the third 'input' shaft.

When accelerating, assume that you're not adding electricity to the MG, and it's sitting still. Power goes out through the sprocket.

Then, you add battery current to the MG, and it starts spinning. Since it is spinning to support the engine, the two rotations are added, and the summed output goes out the sprocket.

Now, at speed, the you let off the gas. The bike starts slowing down, as the moving mass is spinning the generator, and the current gets pushed back into the battery.

There are losses. The planetary gearing is apx. 90% The MG/controller is 70-80% or so efficient at converting battery potential energy into mechanical energy. The MG/Charger/Battery is about 70% efficient at converting mechanical energy into chemical potential energy in the battery. So, for each charge/discharge cycle (Kinetic energy through gearbox through MG through Controller to Battery; Battery through Controller Through MG through Gearbox to Kinetic energy, you end up with about 50% of the kinetic energy you initially started with.

 

[ibdennyak]

Good explanation Loquin. Kind of sounds like a form of parallel connection, while I was playing with more of a series connection. As always, those pesky frictional losses get in the way of happiness.